Jordan's King Abdullah said his government would hunt down the people responsible for the suicide attacks in the capital Amman which killed at least 57 people last night.

The remarks came after the al-Qaida in Iraq terrorist organisation today claimed responsibility for the attacks.

King Abdullah said in a nationally televised address: "We will pursue those criminals and those who are behind them, and we will reach them wherever they are.

"We will pull them from their holes and bring them to justice," he said. "We will confront these cowardly terrorist groups that have no religion or conscience."

A statement from al-Qaida in Iraq, which has not been authenticated, was earlier posted on a website used by militant groups and said Amman was targeted because it was the "backyard" for US operations.

The claim was signed in the name of Abu Musab al-Zarqawi, the leader of al-Qaida in Iraq.

The statement said Amman was "a backyard for the enemies of the faith, the Jews and crusaders...a filthy place for the traitors...and a centre for prostitution".

At least 57 people and more than 100 were wounded when suicide bombers targeted three hotels in the Jordanian capital.

The Grand Hyatt, Radisson and Days Inn hotels were said to be popular with foreigners and many of the guests were involved in the reconstruction of Iraq.

Bassel Tarawneh, a spokesman for the Jordanian government, said the victims included 15 Jordanians, one Saudi, one Palestinian, five Iraqis, three Chinese, one Indonesian and 30 others. Two Palestinian security officials and an Israeli-Arab are also believed to be among the dead.

An Iraqi government spokesman, Laith Kubba, said the attack should warn Jordan that it needed to stop playing host to former members of Saddam Hussein's regime.

"I hope that these attacks will wake up the 'Jordanian street' to end their sympathy with Saddam's remnants ... who exploit the freedom in this country to have a safe shelter to plot their criminal acts against Iraqis," said Mr Kubba.

Police held several people overnight, but it is not clear whether they are suspects or witnesses to the attacks. DNA tests are now being carried out to identify the suicide bombers, said police officials.

The attacks have been widely condemned by the international community.

The foreign secretary Jack Straw said Britain would give Jordan practical help to fight terrorism.

"Jordan's sorrow is our sorrow. Jordan's grief is our grief. Jordan's determination to fight this mindless terrorism is our determination as well," he said from Amman. Mr Straw is due to visit Iraq later today.

Last night, Tony Blair said he was shocked and saddened by the bombings in Jordan.

"Our thoughts and prayers are with the victims and their families. We were deeply grateful for the support of the Jordanian government and people after the attacks in London in July and we stand together in this battle against the scourge of terrorism," said Mr Blair.

Police maintained tight security in the capital today, but land borders have now reopened since the attacks.